Lecture 1 : Multiple phase transitions in a system of hard core rotors on a lattice I
Date & Time : Monday, December 19, 2022 at 15:30 hrs
Lecture 2 : Multiple phase transitions in a system of hard core rotors on a lattice II
Date & Time : Tuesday, December 20, 2022 at 9:30 hrs
Lecture 3 : Multiple phase transitions in a system of hard core rotors on a lattice III
Date & Time : Wednesday, December 21, 2022 at 9:30 hrs
Abstract :
I will discuss the entropy of a set of identical hard objects, of general shape, with each object pivoted on the vertices of a d -dimensional regular lattice, but can have arbitrary orientations. Such a system shows multiple geometrical phase transitions as the spacing of lattice is varied. It is a model for the multiple crytalline phases found in many molecular cystals. I will consider in some detail three illustrative cases: hard linear rods, pivoted at one end, linear rods pivoted at mid point, and circular discs with pivot off-center. For asymmetrically placed pivots, in the range of lattice spacings, the problem reduces to a dimer model at finite negative fugacity. The orientation distribution shows multiple cusp-like singularities as a function of orientations. I will discuss an approximate theory that gives the correct positions, and qualitative behavior of these singularities.
About the Speaker:
D. Dhar obtained his B.Sc. Degree from University of Allahabad (1970), M. Sc. from I. I. T. Kanpur (1972), and Ph.D. from California Institute of Technology (1978). He was in the Department of Theoretical Physics at the Tata Institute of Fundamental Research (1978-2016). Since November 2016, he has been working as an Emeritus Professor at I.I.S.E.R. Pune. He is a fellow of INSA, IAS, and NASI, and TWAS, and the recipient of the Shanti Swarup Bhatnagar prize (1991), J. R. Schrieffer Prize in Condensed Matter Physics (1993), S.N. Bose medal of INSA (2001), TWAS Prize in Physics (2002), and the Boltzmann medal (2022).
This lecture series is part of the discussion meeting Statistical Physics of Complex Systems.